Acute graft-versus-host disease (GvHD) is a primary complication of allogeneic stem cell transplantation, associated with wasting, immunosuppression and specific damage to the intestines, liver and skin. GvHD results from activation of donor T cells from human leukocyte antigen (HLA)-identical or related donors against host tissues. Current therapeutic approaches to mitigate the basic underlying pathology of acute GvHD include immune-suppressive drugs or depletion of T cells from the graft, however these options render severely immunocompromised patients susceptible to infection or neoplastic relapse. As such, attenuation of GvHD- associated pathology while maintaining immune function against residual malignancy or infection is the 'holy grail' of HCST adjuvant therapies. Ceramide Therapeutics proposes the generation and development of anti- ceramide monoclonal IgG antibody as a mechanism-based approach to protect host tissue and prevent or treat acute GvHD. Evidence that ceramide regulates tissue pathophysiology during acute GvhD was obtained using mice deficient in acid sphingomyelinase (ASMase)-mediated ceramide generation as hosts for minor antigen mismatched bone marrow and T cells. Inactivation of host ASMase abrogated tissue damage during GvHD and attenuated the inflammatory response responsible for propagating CTL attack of host tissue, thereby significantly improving survival in mouse models. Investigation into the mechanism of action of hepatocyte apoptosis during GvHD revealed that CTLs induce ceramide generation on the target hepatocyte surface, driving the biophysical reorganization of the exoplasmic membrane into structures called ceramide-rich platforms (CRPs). CRPs are sites where transmembrane apoptotic signal transduction takes place, and are amenable to pharmacologic inactivation. In the current application, we propose to generate a high-affinity neutralizing anti-ceramide IgG for advancement into preclinical development. PUBLIC HEALTH RELEVANCE: Inhibition of acute GvHD-associated pathophysiology while maintaining global immune functioning against residual malignancy and infection is the 'holy grail' of HCST adjuvant therapies. Ceramide regulates tissue pathophysiology during acute GvhD, as genetic deletion of acid sphingomyelinase (ASMase)-mediated ceramide generation abrogated tissue damage during GvHD, attenuated the inflammatory response responsible for propagating CTL attack of host tissue, and significantly improved survival in mouse models. Here we propose the generation of a high-affinity neutralizing anti-ceramide IgG to specifically inhibit GvHD pathophysiology while not impacting global T cell function, for advancement into preclinical development.